This invention has particular application to automatic lubrication systems for supplying lubricant to multiple points of lubrication at predetermined intervals and/or in predetermined amounts. Lincoln Industrial sells such automated systems under the Quicklub®, Centro-Matic®, and Helios® trademarks. The Quicklub® system includes a reservoir for holding a supply of lubricant, a stirrer for stirring the lubricant, and an electric or pneumatic pump for pumping lubricant from the reservoir to one or more progressive metering (divider) valves each of which operates to dispense lubricant to multiple points of lubrication. Reference may be made to U.S. Pat. No. 6,244,387, incorporated herein by reference, for further details regarding an exemplary Quicklub® system. The Centro-Matic® system is similar to a Quicklub® system except that lubricant from the pump is delivered through a single supply line to injectors each operating to dispense a metered amount of lubricant to a single lubrication point. Reference may be made to U.S. Pat. No. 6,705,432, incorporated herein by reference, for further details regarding an exemplary Centro-Matic® system. The Helios® system is a dual line system.
In some lube systems, a known volume of lubricant is typically dispensed during each pump piston stroke. Knowing the volume of lubricant dispensed during a piston stroke enables ready calculation of an aggregate amount of lubricant dispensed and/or a flow rate of lubricant dispensed during a given interval. Under certain conditions, lubricant does not entirely fill the pump cylinder. If lubricant does not fill a total volume of the pump cylinder during each stroke, the aggregate amount of lubricant dispensed and the flow rate cannot be determined absent additional equipment. One such example is when lubricant is required in extreme cold temperatures (e.g., below 20° F.), the lubricant becomes more viscous and frequently results in an inability to draw sufficient suction to fill the pump cylinder. In lube systems where pump operation is controlled by determining the amount of lubricant dispensed or the lubricant flow rate from pump cylinder volume, not filling the cylinder may result in insufficient lubricant being dispensed to the lubrication points. Thus, there is a need for a lube system in which the pump is controlled directly from flow rate measurements.